Field of the Invention
The present invention relates to an image blur correction apparatus which uses a plurality of correction optical systems to correct an image blur.
Description of the Related Art
Conventionally, image pickup apparatuses have been known which use two correction optical systems to correct an image blur. Such an image pickup apparatus has been increasingly required to be capable of performing high-magnification zooming in which a focal length largely varies. In optical image blur correction, where a ratio between a displacement of each correction optical system and that of an image is referred to as an “eccentricity sensitivity k”, the eccentricity sensitivity k is represented by a function containing a focal length f and a photographing magnification 3. A displacement dL of each correction optical system is represented by the following Expression (1) by using the eccentricity sensitivity k and a correction angle θ.dL=k(f,β)×θ  (1)
As can be seen from Expression (1), since the displacement dL of the correction optical system varies depending on the focal length f, it is difficult for a zoom lens whose focal length greatly varies to be capable of, both at a telephoto side and a wide-angle side, ensuring a sufficient correction range and providing a satisfactory control resolution and tracking performance.
Japanese Patent Laid-Open No. (“JP”) 2002-250952 discloses an image blur correction apparatus including two correction optical systems with eccentricity sensitivities different from each other and providing a sufficient image blur correction effect both at the telephoto side and the wide-angle side by switching the correction optical system used for image blur correction depending on a focal length of a lens.
However, since the image blur correction apparatus disclosed in JP 2002-250952 has a configuration intended for still image shooting, the apparatus has the following problem when applied to motion image shooting. That is, image blur correction in the still image shooting primarily aims to correct a vibration which occurs in exposure to reduce a blur in a captured image, which thus means that continuity of control during operations other than the exposure is not a significant issue. On the other hand, as for the image blur correction in the motion image shooting, it is desirable to perform the image blur correction at all times during the shooting in which a motion image is being recorded and thus is important to continuously provide a constant performance rather than momentarily achieving a maximum performance.
JP 2002-250952 discloses the image blur correction apparatus including the two correction optical systems with the eccentricity sensitivities different from each other and configured to switch, depending on the focal length, the correction optical system to be driven. However, it does not disclose a method of keeping continuity of the control when the focal length varies due to a zooming operation or when the correction optical system is switched. Therefore, in the motion image shooting, an unnatural image motion caused by the switching of the correction optical system used for the image blur correction and a wide-blur motion image caused due to a decrease in an image blur correction performance are unavoidably recorded.